Chestnuts are plant belonging to Fagaceae, and it have been cultured in a vast range such as Europe, America, China, Japan and the like. Also, it has been known that chestnuts have abundant vitamin, and is good for digestive rate due to containing 40% of starch, and its nutrition is abundant.
To provide chestnuts having the above-mentioned property as table use, chestnut which had been treated with boiling down or soaking chestnuts with sugar, thereby lowering a moisture activity, to prevent from decomposing it by microorganism, have been provided, or chestnuts which had been treated with sugar and sterilized have been provided. Furthermore, it has been popularized the method that eat boiled chestnuts at raw state. On the other hand, it has been prevailed the method providing to consumer the processed chestnuts by roasting harvested chestnuts, and peeling, and then washing and freezing it followed by packing in a pouch, and then retort sterilizing without a thawing procedure or packing in a pouch with a nitrogen substitution and first sterilizing at high temperature (121° C., 30 minutes) without a thawing procedure.
However, the above-mentioned prior art has a various drawback, for example, generation of an extraordinary taste or smell during a processing procedure since it is provided in state of packing or sterilizing a boiling down or soaking chestnuts with sugar without a thawing procedure, deformity of a shape, propagation of microorganism, and decrease of gusto and functionality by degrading of structure at first sterilizing at high temperature.
To solve the above drawback, Japanese patent early publication Hei 06-209702 discloses a preparing procedure for a processing chestnuts constituted with a step of; peeling harvested chestnuts, and freezing it followed by thawing, and boiling to remove a moisture, and burning to allow an ash color to chestnuts after rapid freezing and heating with far infrared ray, and than soaking chestnuts with sugar followed by rapid freezing it and adding a seasoning and mixing it, and finally packing and then retort sterilizing as itself. Namely, the above-mentioned Japanese patent early publication Hei 06-209702 provide an advantage that it allow to increase sugar content by comprising a heating process with far infrared ray, increase storing capacity, and produce industrially with massive volume.
However, the said prior method is also not economical in aspect of time and cost, and is complex and cumbersome since the procedure is consisted of 9 steps of thawing and boiling process→rapid freezing process→heating process with far infrared ray (230˜280° C., 5˜10 minutes)→burning process to allow an ash color→soaking process in sugar solution→rapid freezing process→adding a seasoning and mixing process→packing process→retort sterilizing process. Furthermore, it has a drawback that a taste and nutritional ingredient of chestnuts is degraded rapidly because of refrigerating storage after peeling a harvested chestnuts, and an original taste and favor of chestnuts is inflicted a lose since, in the method, sugar solution and seasoning is used to improve sugar content and taste of chestnuts.